The Quran
“If you do not aid the Prophet – Allah has already aided him when those who disbelieved had driven him out [of Makkah] as one of two, when they were in the cave and he said to his companion, “Do not grieve; indeed Allah is with us.” And Allah sent down his tranquillity upon him and supported him with angels you did not see and made the word of those who disbelieved the lowest, while the word of Allah – that is the highest. And Allah is Exalted in Might and Wise.” [Qur’an; 9:40]
“…those who walk upon the earth easily and when the ignorant address them harshly, they say words of peace,” [Qur’an; 25:63]
Hadith
Narrated Aisha, Ummul Mu’minin: I never saw anyone more like the Messenger of Allah (peace be upon him) in respect of gravity, calm deportment, pleasant disposition – according to al-Hasan’s version: in respect of talk and speech. [Abu Dawud]
Narrated Anas bin Malik: The Prophet (peace be upon him) said, “Make things easy for the people, and do not make it difficult for them, and make them calm (with glad tidings) and do not repulse (them ). [Sahih Bukhari]
The Prophet (peace and blessings of Allah be upon him) said, “Be gentle and calm, […] as Allah likes gentleness in all affairs.” [Sahih Bukhari]
The Messenger of Allah (peace and blessings of Allah be upon him) said: “The Muslim is the one from whose tongue and hand the people are safe, and the believer is the one from whom the people’s lives and wealth are safe.” [Sunan an Nasa’i]
Abu Huraira reported Allah’s Messenger (peace and blessings of Allah be upon him) as saying. Don’t nurse malice against one another, don’t nurse aversion against one another and don’t be inquisitive about one another and don’t outbid one another (with a view to raising the price) and be fellow-brothers and servants of Allah. [Sahih Muslim]
Narrated Abu Hurairah: that the Messenger of Allah (peace and blessings of Allah be upon him) said: “By the One in Whose Hand is my soul! You will not enter Paradise until you believe, and you will not believe until you love one another. Shall I inform you about a matter which if you do it, then you will love one another? Spread the salam [peace] among each other.” [Tirmidhi]
Abu Hurairah narrated that a man came to the Messenger of Allah (peace and blessings of Allah be upon him) and said: “Teach me something that is not too much for me so that, perhaps, I may abide by it.” He (peace and blessings of Allah be upon him) said: “Do not get angry.” He repeated that (the request) a number of times, each time he replied: ‘Do not get angry.” [Tirmidhi]